59.(Pg. [68]) What is said respecting the composition of all machines, and for what must allowance always be made in estimating their power?
60.(Pg. [69]) What is meant by friction, and what causes it?
61.(Pg. [69]) How may friction be diminished?
62.(Pg. [69]) Friction is of two kinds, what are they?
63.(Pg. [69]) For what purpose are wheels often used?
64.(Pg. [69]) When is the friction of a carriage wheel changed from the rolling to the rubbing friction?
65.(Pg. [70]) What is a medium, and in what proportion does it diminish motion?
66.(Pg. [70]) Under what circumstances must a body be placed, in order to move without impediment?